1. Field
The present invention relates to disk drives for computer systems. In particular, the present invention relates to a disk drive initializing a coil temperature estimation algorithm using a resistance of the coil estimated during a load operation.
2. Description of the Related Art
Disk drives comprise a disk and a head connected to a distal end of an actuator arm which is rotated about a pivot by a voice coil motor (VCM) to position the head radially over the disk. The disk typically comprises a number of concentric data tracks each partitioned into a number of data sectors. Access operations are performed by seeking the head to a target data track, and performing a write/read operation on the data sectors within the data track. The prior art has suggested to estimate the temperature of the coil and adjust the seek time accordingly to prevent the VCM from overheating, which may cause the material molded over the voice coil to delaminate, lose its rigidity, and/or outgas particles that may contaminate the disk. Overheating the VCM may also degrade the strength of the fixed magnets that interact with the magnetic flux generated by the voice coil.
A temperature sensor (e.g., a thermistor) has been employed to estimate the temperature of the coil, however, since the temperature sensor is not integrated with the coil, there may be significant estimation error. In order to improve the estimate, the prior art has suggested to estimate the coil temperature as a function of the power input into the coil (i.e., as a function of the current applied to the coil and its resistance). The coil temperature is estimated by making adjustments to an initial coil temperature estimate which is determined, for example, with a temperature sensor. However, if the initial coil temperature estimate is inaccurate, it may take time for the coil temperature estimation algorithm to converge, leading to undesirable VCM overheating during the convergence period. In addition, if the coil resistance is estimated from the coil temperature estimate (e.g., prior to executing an unload operation), the error in the resistance estimate may cause the disk drive to malfunction.
There is, therefore, a need to improve the coil temperature estimation algorithm in a disk drive.